A variety of support garments are on the market today. The purpose of support garments is to overcome the elevated internal pressures within a human extremity caused by gravity or disease processes. In many individuals the venous valves which normalize the pressure in the veins of a vertically oriented extremity are inherently too few in number, incompetent, damaged, diseased or otherwise poorly functional. In such cases blood must be returned to the heart from the extremities in long, unsegmented columns in which the pressure exceeds the normal pressure for that level and may result in swelling, stasis ulcers, varicose veins, and other vascular and dermatological diseases. Support garments are designed to provide sufficient external circumferential counter pressure to maintain the normal venous and lymphatic pressures at a given leval in the extremity, thus assisting the movement of venous blood and lymphy from the extremity.
There are numerous problems associated with prior art support garments. Commercial prior art support garments are often circular knit (see U.S. Pat. No. 4,086,790); due to limitations in the tubular fabric circumferences a achievable on circular knitting machines, it is impossible to obtain the exact proportional circumferential counter pressures necessary in support stockings and other garments. In order for the support garment to be effective, the counter pressure exerted by the garment preferably must decrease more or less at a predetermined rate from the position of the extremity most distal from the torso and decreasing proximally toward the torso. There have been proposals to place inserts in such circular knit fabrics to relieve the pressures relatively adjacent to the torso; however, even such proposals do not result in a support garment having the maximum desirable counter pressures at that level.
According to the present invention, the problems inherent in prior art support garments are overcome in a simple and easy manner; according to the invention it is possible to produce support garments that have essentially the pressure gradiations characteristics that are desirable for support garments, yet such garments can be produced comparatively inexpensively according to the invention.
In general, the invention provides the manufacture of support garments utilizing cut and sew techniques with warp-knit power fabrics. The prior art is replete with suggestions for formation of stockings in general utilizing cut and sew techniques; however, heretofore such stockings have either (1) not been produced for the purpose of imparting measurable compression, or (2) have not been entirely successful in providing the necessary degree of predictability of the compression due to the presence of an excessive amount of stretch in the longitudinal (as opposed to circumferential) dimension of the garment. With respect to class (1), attention is directed to U.S. Pat. Nos. 2,768,385 and 2,445,049. In these disclosures, the fabric is knit with some stretchable yarn before the cut and sew techniques are practiced; however, the stretchable yarn is not a power yarn, and its only purpose is to oppose the tendency to bag, rather than imparting measurable compression. With respect to class (2), attention is directed to U.S. Pat. No. 2,574,873. Products are produced commercially following the teachings of that patent, utilizing an open power knit fabric having significant stretch and compression in both the longitudinal and circumferential dimensions (the warp and filling directions as originally produced), as being important and necessary. While such products are useful for their intended purposes, it has been found according to the present invention that the substantial longitudinal stretch inherent in such products can change the pre-engineered lateral compressive properties that are desired, with consequent less than perfect functioning of the products.
The method according to the present invention is for the manufacture of support garments for elongated human extremities comprising the steps of providing a sheet of warp-knit power fabric, the fabric having a lengthwise (warp) dimension of greatest stretch and power and a filling dimension in which the stretch is incidental; cutting out of the sheet a support garment form, the sheet being orientated during cutting so that the lengthwise dimension of the sheet extends circumferentially in the final garment produced and so that the filling dimension of the sheet extends longitudinally in the final garment produced; and seaming the edges of the garment formed to produce the final support garment, the seam extending along the dimension of elongation of the extremity on which the support garment is adapted to fit. The "lengthwise" dimension of the warp-knit power fabric is the direction in which during knitting the fabric exits the machine, and the direction in which spandex strands are laid. Such fabrics have a great deal of stretch and power in that direction, and much less in the "width" or cross-machine direction. Preferred warp-knit power fabrics are tricots and raschels having, for example, approximately a 250% warp stretch and only approximately an 80% filling stretch [typical of one-way stretch fabrics]; as opposed to prior art open power net constructions (as in U.S. Pat. No. 2,274,873) having about 200-220% warp or machine direction stretch, and purposefully engineered so as to have about 175-190% filling or cross-machine stretch, or prior art bag-free stockings (as in U.S. Pat. Nos. 2,445,049 and 2,768,385) having little or no compression capability. A fabric stretch of at least about twice as great in the lengthwise (warp) dimension as in the filling dimension is desired. The power yarn is utilized for the purpose of imparting measurable compression and may comprise spandex or rubber or other yarns with the distention properties of spandex. The secondary yearn or yarns which comprise the fabric can be any fiber that is capable of being warp-knit and is compatible with spandex, examples of which are nylon and polyester. According to the present method, the cutting step is practiced so that the compression provided by the garment is greatest at the portion thereof adapted to be most distal from the torso along the human extremity on which it is adapted to be disposed, and the compression accurately and predictably gradually continuously decreases proximally along the extremity toward the torso.
According to the present invention a support garment for an elongated human extremity is provided. The garment comprises a tube of warp-knit power fabric having a dimension (circumferential) in which the greatest stretch and power is provided and a dimension (lengthwise) in which the stretch is incidental (i.e., about 65-80%); the circumference of this tube varying as required so that it conforms in shape to the extremity on which it is adapted to be disposed and a seam formed along the length of the tube in the direction of elongation of the extremity on which it is adapted to be disposed, the seam extending transverse to the lengthwise dimension of the warp-knit power fabric.
It is the primary object of the present invention to provide a relatively inexpensive support garment that has perfect compression gradiations so that the necessary counter pressure is provided along the entire length of the extremity on which the garment is disposed. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.